Emergency lamp



United States Patent EMERGENCY LAMP Harold A. Smethurst, New York, N. Y. Application April 12, 1954, Serial No. 422,473

1 Claim. (Cl. 240-371) The present invention relates to an electric lighting circuit and arrangement, and more particularly to an emergency lighting system.

A well known disadvantage of electric light bulbs of the incandescent type is that they blow out after a time. In some cases, the failure of light at unpredictable times can be dangerous and hazardous as may be readily understood. It is to this general problem that the present invention is directed.

A primary object of this invention is to provide an electric light fixture that can always be depended upon to produce light.

A further object of this invention is to provide an electric lighting arrangement wherein one lamp normally provides light and upon the failure thereof, a stand-by lamp is engaged to provide light.

A further object of this invention is to provide a lighting fixture that is compact, inexpensive to produce and is readily adapted to be received in a conventional electric light socket.

A further object of the present invention is to provide an emergency electric light fixture that will operate with minimum current drain from the source.

These and other objects of this invention will become apparent from the following description taken with the drawings in which Fig. 1 is a cross-section through the light bulb fixture of the present invention, and

Fig. 2 is a diagrammatic view showing the condition of the circuit after the first bulb has burnt out. The present invention contemplates the use of two light bulbs, one of which is normally illuminated when electric power is applied to the fixture. An electromagnetic relay is connected in series with the normally illuminated bulb and is therefore in an energized condition. For purposes of description the normally illuminated bulb will be herein referred to as the master bulb.

Upon failure of the master bulb due to its filament opening, the electromagnetic relay will deenergize to close a pair of contacts to energize a stand-by bulb thereby producing illumination for the area.

Referring now to Figure 1, there is therein shown a cross-section of the fixture generally indicated by numeral 10. The fixture comprises a casing 11 which may be made of Bakelite or other suitable material. The casing has two openings adapted to receive two light bulbs 12 and 13. The' inner walls of the openings have two threaded sheet metal shells 14 and into which the light bulbs 12 and 13 are screwed. It should be noted that the shells 14 and 15 are electrically connected as at 16.

One end of the fixture has a threaded sheet metal shell 17 fastened to the outer periphery. thereof whereby the entire fixture may be received in a conventional electric light socket. A wire 18 connects shell 17 with shell 15. A contact member 19 is secured within the fixture and so located that one end thereof contacts the center contact of master bulb 12 as shown. The other 2,735,928 Patented Feb. 21, 1956 ice end of contact member 19 is connected to one end of coil 21 by wire 22. The other end of coil 21 is connected by wire 23 to a center contact point 24 at the bottom of the fixture.

Another contact member 25 is fastened to the fixture in a position whereby one end is engaged by the center contact of stand-by lamp 13. The armature 26 of the relay 21 is connected to the lower lead of the coil as clearly shown in Fig. 2 and is adapted to contact the member 25 to complete a circuit to be described.

A capacitor 27 is connected to center contact 24 and to shell 17 by wire 28. This capacitor may be of a value of one microfarad and acts as a filter to prevent any high frequency potentials that might arise from being fed back into the line. Another capacitor 29 is connected across the relay coil to minimize current drain by the coil. The capacitor may be in the order of 4 microfarads.

With the fixture inserted in an electric light socket, power is applied to contact 24 and shell 17. A circuit may be traced from shell 17, wire 18, shell 15, shell 16, the filament of lamp 12, center contact of lamp 12, contact member 19, wire 22, relay coil 21, wire 23 to contact 24. It is seen that master bulb 12 is illuminated and coil 21 is energized to maintain armature 26 in the position shown in Fig. 1. When the filament of master lamp 12 breaks, the above traced circuit is opened to deenergize relay 21 which thereupon releases its armature 21 to contact member 25 as seen in Fig. 2. A circuit may now be traced from shell 17, wire 18, shell 15, the filament of stand-by lamp 13, member 25, armature 26, wire 23 to center contact 24. In this condition, the stand-by lamp is illuminated. When the burned-out master lamp 12 is replaced by a good one, the circuit through relay 21 is reestablished to deenergize stand-by lamp 13 permitting the replaced master lamp 12 to supply the light.

While the present invention has been disclosed with respect to a specific embodiment thereof, it is understood that various modifications may be made without departing from the scope and spirit of the invention as set forth in the appended claim.

Having described my invention, what I claim as new is:

An electric light fixture including a hollow casing having two openings in one end thereof with sheet metal shells in the openings and a center contact at the opposite end of said casing, two capacitors connected in parallel to the center contact, an external threaded sheet metal shell upon the same end of the casing with said center contact and connected in series with one of the capacitors and the latter also connected to one of the two sheet metal shells, both of the shells being adapted to receive the bases of two lamps so that the center contacts of the lamps project into the casing, a stationary contact in the latter making contact with the center contact of one lamp, a relay coil within the casing connected at one end with said stationary contact and at the other end with the other of the two capacitors, a movable armature for said coil connected at one end with the last mentioned capacitor and overlying the other end of said coil, a second contact within said casing disposed in the path of the armature when the same is released by the coil and having an end thereof in active contact with the other of the two lamps, and means interconnecting the two metal shells receiving the two lamps.

References Cited in the file of this patent UNITED STATES PATENTS 1,483,726 Heitz Feb. 12, 1924 1,542,768 Heitz June 16, 1925 1,581,209 Heitz Apr. 20, 1926 

